Interesting substrate-temperature dependence on surface-enhanced Raman scattering

We report here an interesting phenomenon that surface-enhanced Raman scattering (SERS) intensity can be significantly improved on electrochemically roughened silver substrates at slightly elevated temperatures. Experimental results indicate that the SERS enhancement capabilities are gradually raised from 25 °C to a maximum at 50 °C and monotonically decreased from 50 to 60 °C. The SERS of Rhodamine 6G (R6G) adsorbed on the SERS-active substrate at 50 °C exhibits a higher intensity by 7-fold of magnitude, as compared with that of R6G adsorbed on the SERS-active substrate at 25 °C. More interestingly, this phenomenon is reversible. The SERS intensity of R6G was also decreased to its original level when the temperature of the elevated substrate was reduced from 50 to 25 °C. These interesting phenomena are valid for all different target molecules generally used in SERS studies. Further experiments reveal that the increase in SERS enhancement capability of SERS-active Ag substrates at slightly elevated temperatures may mainly comes from the corresponding increase of the chemical (CHEM) enhancements.